The major objective of the proposed research is the characterization of a single-locus genetic effect that influences behavioral performance in a learning situation. The proposed analysis should determine whether the locus being characterized influences performance by affecting stimulus sensitivity, activity level, responses to initial conditioning trials, or perhaps learning ability. The generality of the effect among various genotypes and upon other behaviors will also be assessed. The primary genetic methods will be Mendelian analysis and a new technique, the recombinant-inbred strain technique. Behavior will be assessed in active and passive avoidance situations, activity wheels, the open-field, water mazes, and operant-conditioning avoidance situations.